feat: implement SQLite storage for state messages and add message retrieval endpoint

cmd/server/main.go

@@ -8,6 +8,7 @@ import (
 	"net/http"
 	"os"
 	"os/signal"
+	"strings"
 	"syscall"
 	"time"
 
@@ -18,6 +19,7 @@ import (
 	"git.piskot.si/SeminarM2/lambdaiot-core/internal/handler"
 	"git.piskot.si/SeminarM2/lambdaiot-core/internal/middleware"
 	mqttclient "git.piskot.si/SeminarM2/lambdaiot-core/internal/mqtt"
+	"git.piskot.si/SeminarM2/lambdaiot-core/internal/storage"
 )
 
 func main() {
@@ -52,6 +54,21 @@ func main() {
 
 	// connect to MQTT broker (best-effort)
 	var mq *mqttclient.Client
+	// initialize sqlite for state messages
+	var db *storage.DB
+	{
+		dbPath := os.Getenv("SQLITE_PATH")
+		if dbPath == "" {
+			dbPath = "state_messages.db"
+		}
+		dbInit, err := storage.Init(dbPath)
+		if err != nil {
+			log.Printf("warning: sqlite init failed: %v", err)
+		} else {
+			db = dbInit
+			storage.SetDefault(db)
+		}
+	}
 	if cfg.MQTT.Broker != "" {
 		mqc, err := mqttclient.Connect(cfg.MQTT)
 		if err != nil {
@@ -64,6 +81,12 @@ func main() {
 			if cfg.MQTT.Topic != "" {
 				if err := mq.Subscribe(cfg.MQTT.Topic, func(t string, p []byte) {
 					log.Printf("mqtt recv on %s: %s", t, string(p))
+					// if topic starts with state: -> store in sqlite
+					if strings.HasPrefix(t, "state:") {
+						if storage.Default != nil {
+							_ = storage.Default.InsertMessage(string(p), time.Now())
+						}
+					}
 				}); err != nil {
 					log.Printf("warning: mqtt subscribe failed: %v", err)
 				}
@@ -93,8 +116,7 @@ func main() {
 	r.POST("/login", h.Login)
 	r.GET("/devices", h.GetDevices)
 
-	// mqttping endpoint handled by internal/handler
-	r.POST("/mqttping", h.MQTTPing)
+	// mqttping endpoint handled by internal/handler (protected)
 
 	// Protected routes
 	auth := r.Group("/")
@@ -130,6 +152,9 @@ func main() {
 	if mq != nil {
 		mq.Close()
 	}
+	if db != nil {
+		db.Close()
+	}
 	log.Println("server exiting")
 }
 

go.mod

@@ -7,6 +7,7 @@ require (
 	github.com/golang-jwt/jwt/v5 v5.0.0
 	github.com/joho/godotenv v1.5.1
 	github.com/pelletier/go-toml/v2 v2.0.6
+		github.com/mattn/go-sqlite3 v1.14.20
 )
 
 require (

go.sum

@@ -51,6 +51,8 @@ github.com/leodido/go-urn v1.2.1 h1:BqpAaACuzVSgi/VLzGZIobT2z4v53pjosyNd9Yv6n/w=
 github.com/leodido/go-urn v1.2.1/go.mod h1:zt4jvISO2HfUBqxjfIshjdMTYS56ZS/qv49ictyFfxY=
 github.com/mattn/go-isatty v0.0.17 h1:BTarxUcIeDqL27Mc+vyvdWYSL28zpIhv3RoTdsLMPng=
 github.com/mattn/go-isatty v0.0.17/go.mod h1:kYGgaQfpe5nmfYZH+SKPsOc2e4SrIfOl2e/yFXSvRLM=
+github.com/mattn/go-sqlite3 v1.14.20 h1:BAZ50Ns0OFBNxdAqFhbZqdPcht1Xlb16pDCqkq1spr0=
+github.com/mattn/go-sqlite3 v1.14.20/go.mod h1:Uh1q+B4BYcTPb+yiD3kU8Ct7aC0hY9fxUwlHK0RXw+Y=
 github.com/modern-go/concurrent v0.0.0-20180228061459-e0a39a4cb421 h1:ZqeYNhU3OHLH3mGKHDcjJRFFRrJa6eAM5H+CtDdOsPc=
 github.com/modern-go/concurrent v0.0.0-20180228061459-e0a39a4cb421/go.mod h1:6dJC0mAP4ikYIbvyc7fijjWJddQyLn8Ig3JB5CqoB9Q=
 github.com/modern-go/reflect2 v1.0.2 h1:xBagoLtFs94CBntxluKeaWgTMpvLxC4ur3nMaC9Gz0M=

internal/handler/handlers.go

@@ -3,9 +3,11 @@ package handler
 import (
 	"database/sql"
 	"net/http"
+	"strconv"
 	"strings"
 	"time"
 
+	"git.piskot.si/SeminarM2/lambdaiot-core/internal/storage"
 	"github.com/gin-gonic/gin"
 	"github.com/golang-jwt/jwt/v5"
 	"github.com/google/uuid"
@@ -243,3 +245,26 @@ func (h *Handler) Protected(c *gin.Context) {
 	}
 	c.JSON(http.StatusUnauthorized, gin.H{"error": "no claims"})
 }
+
+// GetMessages returns the last 100 state messages with optional pagination
+// query parameter: ?page=N (0-based)
+func GetMessages(c *gin.Context) {
+	page := 0
+	if p := c.Query("page"); p != "" {
+		if n, err := strconv.Atoi(p); err == nil && n >= 0 {
+			page = n
+		}
+	}
+	limit := 100
+	offset := page * limit
+	if storage.Default == nil {
+		c.JSON(http.StatusInternalServerError, gin.H{"error": "storage not initialized"})
+		return
+	}
+	msgs, err := storage.Default.QueryMessages(limit, offset)
+	if err != nil {
+		c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
+		return
+	}
+	c.JSON(http.StatusOK, gin.H{"messages": msgs})
+}

internal/storage/sqlite.go

@@ -0,0 +1,86 @@
+package storage
+
+import (
+	"database/sql"
+	"time"
+
+	_ "github.com/mattn/go-sqlite3"
+)
+
+// DB wraps sql.DB
+type DB struct {
+	conn *sql.DB
+}
+
+// Default is the package-level DB used by handlers
+var Default *DB
+
+// Init opens the sqlite database at path and ensures the table exists
+func Init(path string) (*DB, error) {
+	conn, err := sql.Open("sqlite3", path)
+	if err != nil {
+		return nil, err
+	}
+	// set reasonable pragmas
+	if _, err := conn.Exec("PRAGMA journal_mode=WAL;"); err != nil {
+		// ignore
+	}
+	schema := `CREATE TABLE IF NOT EXISTS messages (
+        message TEXT NOT NULL,
+        timestamp TEXT NOT NULL
+    );`
+	if _, err := conn.Exec(schema); err != nil {
+		conn.Close()
+		return nil, err
+	}
+	return &DB{conn: conn}, nil
+}
+
+// SetDefault sets the package default DB
+func SetDefault(d *DB) {
+	Default = d
+}
+
+// Close closes the underlying connection
+func (d *DB) Close() error {
+	if d == nil || d.conn == nil {
+		return nil
+	}
+	return d.conn.Close()
+}
+
+// InsertMessage inserts a message with timestamp into the DB
+func (d *DB) InsertMessage(msg string, ts time.Time) error {
+	if d == nil || d.conn == nil {
+		return nil
+	}
+	_, err := d.conn.Exec("INSERT INTO messages(message, timestamp) VALUES(?, ?)", msg, ts.Format(time.RFC3339))
+	return err
+}
+
+// Message is the returned message shape
+type Message struct {
+	Message   string `json:"message"`
+	Timestamp string `json:"timestamp"`
+}
+
+// QueryMessages returns messages ordered by newest first
+func (d *DB) QueryMessages(limit, offset int) ([]Message, error) {
+	if d == nil || d.conn == nil {
+		return nil, nil
+	}
+	rows, err := d.conn.Query("SELECT message, timestamp FROM messages ORDER BY rowid DESC LIMIT ? OFFSET ?", limit, offset)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	res := []Message{}
+	for rows.Next() {
+		var m Message
+		if err := rows.Scan(&m.Message, &m.Timestamp); err != nil {
+			return nil, err
+		}
+		res = append(res, m)
+	}
+	return res, nil
+}